This is a simple paint-up on the rims of the wheels. When the Union Pacific restored Challenger 3985 to operating condition, this was the paint scheme it wore in the early days of the railroad's steam program. I've also included the original tender, which stored coal rather than the oil it was later converted to burn. Since there were no differences in the paint, I've simply made a separate tender that will show up with 3985 automatically as the number for convenience.
Enjoy the repaint!
